Printer ink tanks contain a volume of ink for printers. Large format ink tanks are ink tanks for large format printers and typically contain relatively large volumes of ink, for example of more than one liter of ink. Existing examples of large format ink tanks are arranged to be emptied into permanent ink tanks in the large format printer. This creates a risk that ink is spilled. Other existing example ink tanks are arranged to be fluidically connected to the printer and supply ink to the printer in a connected state. Such ink tank is placed on, or close to, the printer during usage, and connected to an ink inlet. The ink is drawn from the ink tank by a pump or other ink suction device wherein an internal bag flexes to compensate for a changing backpressure in the bag.